


Underbody

by FreddyFazbutt



Category: Osmosis Jones (2001), Undertale (Video Game)
Genre: But Osmosis Jones is here to help, Chapters switch between Frisk on the outside and Chara on the inside, Crossover, Frisk Gets Sick, Frisk has adventures too, Frisk's digestive system is magical, Gen, POV Chara, POV First Person, POV Frisk, POV Second Person, The Characters Of Undertale go inside Frisk
Language: English
Status: In-Progress
Published: 2017-06-09
Updated: 2017-06-19
Packaged: 2018-11-11 13:37:46
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 1,578
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11149527
Author URL: https://archiveofourown.org/users/FreddyFazbutt/pseuds/FreddyFazbutt
Summary: Frisk comes down with a flu and rests for a few days but a question from Papyrus has the monsters journey inside Frisk to learn about human anatomy and along the way will meet a certain red blood cell that seems very familar....





	1. Sick - Frisk

**Author's Note:**

> This story is kind of weird but I hope you enjoy nonetheless

  1. You were in bed coughing when Toriel opened the door to discover you hadn't got out of bed and said "Hmm it seems someone is sick" You tried to deny it but you knew you couldn't fool Toriel.




Toriel kissed you on the forehead and called everybody in to visit you which made you smile after you had promised Sans no more resets things had changed drastically. Everything became much more advanced and there wasn't much war anymore. The monsters came in and asked you a question which would change things.

They were standing in your room and Papyrus asked "HUMAN FRISK I WAS WONDERING HOW YOU GET SICK AND UNSICK" You shrugged after all you didn't know yourself then Alphys said There is only one way to find out and pulled out a gun which was blinking green and had wires sparking from it.

You realized this was a shrink ray and asked where she got it from but all she said was "I built it for fun" You shrugged as Toriel brought in your favorite soup which was Chicken Noodle and set it on your nightstand and left.

Alphys said "Wanna go on a adventure?" You watched as everyone seemed to be in agreement then nodded when Alphys looked at you and handed you the shrink ray and she said "This might be weird but we are going to stand on your bed and you then press the trigger and shrink us.

You nodded and waited until they were all on the bed before pressing the trigger and watching them shrink to a size where you could no longer see them. You held out your hand and felt the feeling of tiny bodies sit on your hand and when you had them all.

You dropped them into the soup and picked up your spoon then opening your mouth you shoved the spoon into your mouth and swallowed which sent them into your stomach.


	2. Eaten - Chara

**Summary for the Chapter:**

> Chara and the monsters get swalllowed and enter Frisk's body

I was visiting Frisk with the monsters when I heard Papyrus ask the question and I gulped as Alphys produced a actual shrink ray with which to shrink us and my thoughts were immediately turned to the fact that Frisk was actually going to eat us.

It made me feel weird and I didn't understand it but there was no time as Alphys handed Frisk the shrink ray and we got on their bed and Frisk aimed it at us. Once Frisk was sure they would hit all of us they fired and a green blast of energy hit us.

Suddenly Frisk and their bed seemed to get bigger and bigger until we stood on the bed. Everything was huge including Frisk who put their hand down for us to climb on which actually seemed to be hard to do.

Finally we had all climbed to their hand and everything began moving as they dropped us into the soup that Toriel had brought and picked up a spoon and dipped the spoon in the soup and scooped us up.

Then opening their mouth which was full of teeth they stuck the spoon in and all of a sudden my surroundings became wet and fleshy as we were now in Frisk's mouth. We were pushed off the spoon by Frisk's tongue and Sans said "man kid's got some teeth"

There was nodding from everyone except me as suddenly we were pushed down Frisk's throat by their tongue when they swallowed. As they swallowed we were pushed down into their stomach where we dropped onto a piece of pie most likely from last night.

Suddenly a crackling turned our attention to strange bone creatures who appeared to be eating the fat off the pie and I looked around. Frisk's stomach appeared to have magical qualities which was weird


	3. The start of a sick child's adventure - Frisk

**Summary for the Chapter:**

> Frisk starts their own adventure with the help of the shrink ray

You sat there coughing when you realized how much fun you could have with a shrink ray and you were filled with DETERMINATION as you picked up the shrink ray and hopped out of bed.

You still had to careful though Toriel was still normal size and could catch you and send you back to bed. So you snuck out the back door while smiling and decided to shrink some people that were bad so you could make them good.

Still in your blue and purple onesie you scanned the streets in search of a injustice and spotted two muggers trying to steal a woman's purse and aimed the shrink ray at the muggers.

You then fired and it hit them shrinking them to the size of ants then you rushed over and picked up the two tiny muggers and put them in your onesie's front pocket.

You did this until you had an ample supply of bad people to use your pacifism ways on and went back to your house where Toriel was sleeping and snuck back into your room with a wriggling pocket full of bad tiny people.

You then spilled the pocket of people onto your bed and sat in front of the pile of people and said "Hello there little guys I'm Frisk your new master" The tiny people began laughing until you took your spoon and said "You will not laugh unless you want me to eat you"

That got them to shut up quick as they listened "I'm going to play with you guys and teach you how to be nice to each other" and you decided to the first game you wanted to play was House so you pulled out your doll house and sat back down on the bed and said "We are going to play house" and for the next hour thats what you did until Toriel came back.

You gulped as Toriel said "Frisk my child who bought you those tiny action figures?" You replied "Sans" Toriel nodded and said "Time for good little Frisks to take a nap"

You whined but Toriel wasn't budging as she took the doll house off your bed and placed your new "toys" in your arms which being that you were still a child made you snuggle up and fall asleep.


	4. A strange encounter - Chara

**Summary for the Chapter:**

> We meet Osmosis Jones and what has been going on inside Frisk

**Notes for the Chapter:**

> This is where the crossover starts to take affect

We watched the bone creatures devour the pie and were about to leave when suddenly none of us could move. Sans and Asgore tried to break free but that was the least of our worries as the bone creatures turned to us and they started running at us when they were whipped by a blue blur.

I could only watch as our rescuer fought off the bone creatures until they left deciding not to tangle with us anymore. We were greeted with the sight of the weirdest person i'd ever seen Asgore said "Thanks for saving us but what were those things?" The man? said "Just a bunch of Foodbreakers they are common in our host"

I asked "Who are you how did you get in here and why do you know that?" He chuckled and said "Osmosis Jones white blood cell to one Frisk Dreemurr I am part of Frisk and yet i'm not" I gasped but Sans said "How do you know their name?" He said "We have to when we run their body to keep it working right I'll show you" He then whistled and a car drove up.

I was at a loss for words as we got in the car which drove into what I assumed was their bloodstream except it looked more like a city than anything else there was legitimate buildings made of the blood vessels.

We were driven to a quaint house and Ozzy said "I used to have a friend living here but he took off and I haven't seen him since" We got out of the car and were led into a house where pizza sat on the table most likely from last night. Alphys asked "Why haven't we ever seen this?" Jones said "We are microscopic and hidden well enough that you wouldn't"

He then smiled at us and said "so you can stick around until I give you the tour but then you gotta leave okay?" I asked "Why?" He said "Because there is a virus around and he'll make you Outsiders sick too and not only that but you're not supposed to be here the police will catch you" Asgore said "But you are police!" He nodded and said "I'm one of the few that doesn't fear Outsiders"

We spent the rest of what was considered night down here and fell asleep in some guest rooms. When we awoke from our sleep Osmosis Jones had a trenchcoat on and he said "Time for that tour I promised" and he drove us to Frisk's brain.

He said "This is Frisk's brain where we keep their intelligence going 100% they are very intelligent for their age so we have a lot of workers stationed here"

Next he showed us their eyes and we could see for the first time how they saw and it was weird their sight was perfect but the screens were not as narrow as they appeared. Next he showed us their digestive system even a video of them going pee and I almost lost my lunch.

Our final stop was their nose which was gooey and gross he said "And this is their nose and your ticket out of here" but before anything could happen a hand knocked him out and suddenly we were knocked out cold the last thing I heard was "Hello Jones"


End file.
